I. Field of the Present Invention
The present invention relates generally to structural support rails, and more particularly, to a novel, elongated beam having an internal web and a high strength-to-weight ratio which is especially advantageous for incorporation in the construction of a motor vehicle underbody.
II. Description of the Prior Art
Previously known motor vehicle chassis constructions include a frame which is often constructed of longitudinal rails. Such rails are often connected by cross braces or the like to form a rigid structure for supporting the running gear, such as the axles, wheels, suspension and brakes, the drive train including the engine and transmission and any transfer case or differential housing, and a separate vehicle body, including passenger compartment components. Such rails must be substantially rigid so as to avoid deformation and bending during operation of the motor vehicle. As a result, it has been known to form the rails from tubular or channel members to provide a high strength per unit area of rail. Unfortunately, such rails often have thick walls, which while adding strength to the frame, are weighty structures which when combined with the cross rails, running gear, drive train and body result in a heavy vehicle structure. As a result, performance characteristics and fuel economy of the motor vehicle can be substantially impaired by having to carry heavy structure and/or components.
One previously known means for reducing the vehicle weight has been to incorporate body panels or an entire body structure as a reinforcing member for the basic frame rails. While such construction reduces the number of parts used in constructing the vehicle and thus reduces the weight of the finished vehicle, such a construction can be substantially more complicated and difficult. For example, it can be difficult to properly assemble the suspension and drive train components in proper alignment unless the frame and body components are fully assembled so that they can provide proper support for the aligned components. Nevertheless, complete assembly of the body and frame rails can complicate the installation of the various components by substantially reducing access to mounting locations for various parts, and requiring complicated manipulation of welding heads, tools and the like to assemble the vehicle. Thus, it becomes extremely difficult to automate the assembly of the vehicle.
In addition, concern for the capability and durability of a motor vehicle has prompted an increase in the thickness or size of materials used in constructing various portions of the vehicle, and particularly, the structure defining the passenger compartment of the vehicle. However, merely increasing the thickness or dimensions of the components used to construct the vehicle works against the interest of reducing weight and fuel consumption, conserving fuel resources and improving performance of the vehicle. Furthermore, the use of exotic, strong but lightweight materials, such as synthetic or natural composite materials are often unduly expensive for use in the mass production of vehicles.